RU2155968C2 - Unit measuring intensity of magnetic field - Google Patents

Abstract

FIELD: magnetic measurements. SUBSTANCE: unit measuring intensity of magnetic field incorporates generator of rectangular pulses, ferrosonde with core made of permalloy with hysteresis loop with squareness ratio close to one to which output winding integrator is connected. Output of integrator is coupled to input of amplifier whose output is connected to input of threshold unit. First logic AND gate is connected in series with first reversible pulse counter, digital-to-analog converter, controlled source of current and excitation winding of ferrosonde. Second input of first reversible pulse counter and first input of first logic AND gate are connected to output of threshold unit. Proposed unit is supplemented with second logic AND gate and second reversible pulse counter. Output of generator is connected to first inputs of second logic AND gate and second reversible pulse counter, output of second logic AND gate is linked to second inputs of first logic AND gate, second reversible pulse counter and key. Third input of second reversible pulse counter is connected to output of first reversible pulse counter and its output is linked to second input of second logic AND gate. EFFECT: increased speed of response thanks to preservation of relative pulse duration proportional to amplitude of pulses. 2 dwg

Description

 The invention relates to magnetic measurements and is intended to measure magnetic field strength.

A known magnetometer comprising a generator, a nuclear magnetic resonance sensor, an amplifier, a frequency controller, a code-voltage converter, an error signal receiver, a level discriminator, a reversible counter, a recording device / ed. St. USSR ¹ 580536, class G 01 R 33/08, 1977 /. However, due to the large size of the nuclear magnetic resonance sensor, the device does not allow measuring magnetic fields in small volumes and at a small distance from the surface of ferromagnetic bodies, i.e. This device cannot be used to test samples of ferromagnetic materials.

A device containing a flux-gate is also known, in the magnetizing winding of which is included a square-wave generator and series-connected shift and reference resistors, in parallel with which a measuring device is connected, and a series-connected amplifier, integrator, threshold unit, and indicator device are connected in series to the output winding of the flux-gate. The device allows you to measure large fields near the surface of ferromagnetic bodies by the compensation method / auth. USSR ¹ 525902, class G 01 R 33/02, 1976 /. The disadvantage of this device is the long measurement process due to manual adjustment of the amplitude of the compensating field.

 Closest to the technical nature of the claimed device is selected as a prototype device for measuring the intensity of the magnetic field / auth. USSR N 815690, class G 01 R 33/02, 1981 /, containing a rectangular pulse generator, a flux gate with a core made of permalloy with a hysteresis loop with a square factor close to unity, to the output winding of which an integrator is connected, with an output connected to an amplifier input, the output of which is connected to the input of the threshold block, and the measuring device, as well as a series-connected logical element AND-NOT, a reversible pulse counter, a digital-to-analog converter, a controlled current source and a key, the second input of a reverse the pulse counter and the first input of the AND gate are connected to the output of the threshold block, the second input of the AND gate is connected to the output of the rectangular pulse generator, the output of the digital-to-analog converter is connected to the input of the measuring device. The second key input is connected to the output of the rectangular pulse generator, and the key output is connected to the magnetizing winding of the flux gate.

раз (Q - скважность импульса). Генератор, входящий в состав данного устройства, генерирует импульсы с постоянной частотой и длительностью, а значит и постоянной скважностью Q. Эта скважность Q должна соответствовать максимальной амплитуде компенсирующих импульсов. Это значит, что скважность Q всегда завышена, т.е. время измерения не минимально возможное. Бели осуществлять регулирование скважности Q в процессе изменения амплитуды компенсирующих импульсов, то время измерения можно значительно сократить.A disadvantage of the known device is the following. The amplitude of the current pulse supplied to the excitation coil of the flux gate can exceed the value of the direct current flowing through the same winding, in

times (Q - pulse duty cycle). The generator, which is part of this device, generates pulses with a constant frequency and duration, and hence a constant duty cycle Q. This duty cycle Q should correspond to the maximum amplitude of the compensating pulses. This means that the duty cycle Q is always overestimated, i.e. measurement time is not the minimum possible. If they regulate the duty cycle Q in the process of changing the amplitude of the compensating pulses, then the measurement time can be significantly reduced.

 An object of the invention is to increase performance by maintaining the duty cycle of compensating pulses proportional to their amplitude.

 The problem is solved using a device for measuring the magnetic field strength, containing a rectangular pulse generator, a flux gate with a core made of permalloy with a hysteresis loop with a square factor close to unity, to the output winding of which an integrator is connected, with an output connected to the input of the amplifier, the output of which connected to the input of the threshold block, the first logical element AND, the first reversible pulse counter, digital-to-analog converter, connected in series a controlled current source, a key, and a flux-gate excitation winding, the second input of the first reversible pulse counter and the first input of the first logic element And connected to the output of the threshold block, additionally equipped with a second logical element And and a second reversible pulse counter. Moreover, the output of the generator is connected to the first inputs of the second logical element And and the second reversible pulse counter, the output of the second logical element And is connected to the second inputs of the first logical element And, the second reverse pulse counter and key, the third input of the second reversible pulse counter is connected to the output of the first reversible counter pulses, and the output to the second input of the second logical element I.

 Comparative analysis with the prototype shows that the inventive device is characterized by the presence of new blocks: the second logical element And and the second reversible pulse counter and their connections with the rest of the circuit elements.

 Thus, the claimed device meets the criteria of the invention of "novelty."

 Comparison of the proposed solutions with other technical solutions shows that the logical element And and the reversible pulse counter are widely known.

 However, when they are introduced in this connection with the other elements of the circuit into the inventive device for measuring the magnetic field strength, the above blocks exhibit new properties, which leads to increased performance by maintaining the duty cycle of compensating pulses proportional to their amplitude. This allows us to conclude that the technical solution meets the criterion of "significant differences".

 In FIG. 1 shows a block diagram of a device for measuring magnetic field strength; in FIG. 2 - time diagrams of the operation of the device.

 A device for measuring the magnetic field strength (Fig. 1) contains a rectangular pulse generator 1, a flux gate 2 with a core made of permalloy with a hysteresis loop with a square factor close to unity, to the output winding of which 3 an integrator 4 is connected, with an output connected to the input of the amplifier 5, the output of which is connected to the input of the threshold unit 6, the first logical element And 7, the first reversible pulse counter 8, the digital-to-analog converter 9, a controlled current source, are connected in series 10, the key 11 and the excitation winding 12 of the flux-gate 2, and the second input of the first reversible pulse counter 8 and the first input of the first logic element And 7 are connected to the output of the threshold unit 6, as well as the second logic element And 13 and the second reversible pulse counter 14. Moreover, the output the generator of rectangular pulses 1 is connected to the first inputs of the second logical element And 13 and the second reverse counter of pulses 14, the output of the second logic element And 13 is connected to the second inputs of the first logical element And 7, the second reverse th pulse counter 14 and key 11, the third input of the second reversible pulse counter 14 is connected to the output of the first reversible pulse counter 8, and the output to the second input of the second AND gate 13.

 The device operates as follows.

The flux gate 2 is placed in a constant or time-varying measured field H _ISM (Fig. 2). The state of the core of the flux gate 2 is determined by the magnitude of the field H _ISM and the value of the compensating pulse field H _k created by the current in the excitation winding 12 of the flux gate 2. The amplitude of the rectangular pulses of the compensating field is proportional to the current of the controlled current source 10, switched by key 11, and their repetition rate is to the output code of the first reversible pulse counter 8. For normal operation of the device, the measured and compensating fields are directed in the opposite direction. The voltage pulses induced in the output winding 3 of the flux gate 2 during the magnetization reversal of its core (U3 in Fig. 2) are integrated by the integrator 4, the voltage at the output of the integrator 4 (U4 in Fig. 2) is proportional to the changes in the induction in the core of the flux gate 2. Amplified by the amplifier 5 the pulses are fed to the input of the threshold block 6, configured in such a way that pulses at its output appear if the changes in the induction in the core of the flux-gate 2 exceed a value equal to the maximum induction of the hysteresis loop of the core material (U6 by of 2). The core of the flux-gate 2 is made of permalloy with a hysteresis loop with a rectangular coefficient close to unity, i.e. the value of the maximum induction of the core material is practically independent of the magnetic field strength and is equal to the value of the residual induction B _r (Fig. 2). Thus, if the measured field H _edited smaller amplitude compensating field H _k, at the output of the threshold unit 6, a pulse (tl, t3 2) acting on the input "subtraction" first reversible pulse counter 8 and to one input of the first NAND gate And 7, prohibiting the effect of a pulse from the output of the second logical element And 13 through the first logical element And 7 to the input “summing” of the first reversible pulse counter 8. As a result, the code recorded in the first reverse pulse counter 8 is reduced, the voltage is in During analog converter 9 and a current controlled source 10. If the measured field H greater than the amplitude of the compensating _{edited to} H, the output of the threshold unit 6 does not appear pulse (t2, t4 Figure 2), and the pulse output from the second AND gate 13 acts via the first logical element And 7 to the input "summation" of the first reversible pulse counter 8, resulting in an increase in the number recorded in it, as well as the voltage at the output of the digital-to-analog converter 9 and the current of the controlled current source 10. Thus, the amplitude uda of the compensating field H _k automatically monitors the magnitude of the measured field strength H _ISM , and the digital code at the output of the primary reversing counter 8 is directly proportional to the value of the compensating field, and therefore the measured field H _ISM .

Consider the process of regulating the pulse repetition rate of the compensating field H _to .

 In the process of operation of the device periodically (by a signal from the output of the second logical element And 13 to the input "record" of the second reverse pulse counter), a digital code is recorded from the output of the first reverse pulse counter 8 to the second reverse pulse counter 14. From the output of the generator 1 pulses are received at the input "subtraction" of the second reversible pulse counter 14, gradually reduce this code. Until the digital code of the second reverse pulse counter 14 becomes less than zero, from its output "<0" to the input of the second logical element And 13 a logical level is received that prohibits the passage of pulses from the output of the generator 1 to the output of the second logical element And 13. As soon as the digital code of the second reverse pulse counter 14 becomes equal to zero, the next pulse after this moment from the output of the generator 1 will lead to the appearance of a signal at the output "<0" of the second reverse counter 14 of the logic level, allowing passage ix pulse output from the oscillator 1 to the output of the second AND gate 13.

 This pulse opens the key 11, allowing the flow of the current pulse from the output of the controlled current source 10 to the excitation winding 12 of the flux-gate 2; the “addition” of the first reversible pulse counter 8 is input through the first logical element And 7 (if there is permission at the output of threshold block 6), increasing its output code; enables the recording of the digital output code of the first reverse pulse counter 8 in the second reverse pulse counter 14.

 Then the process is repeated. Thus, the time interval between the appearance of the compensating field pulses is proportional to the output code of the first reversible pulse counter 8, and hence the amplitude of the compensating pulses ([t1, t2) ≈ Hкt1, [t2, t3] ≈ Hкt2).

The blocks included in the device for measuring the magnetic field can be performed, for example:
rectangular pulse generator, integrator, amplifier, threshold block, first and second logic elements AND, first and second reversible pulse counters, digital-to-analog converter, key, first and second RS-triggers, T-trigger, OR logic element, as described in / Yakubovsky S.V., Barkanov N.A., Kudryashov B.P. Analog and digital integrated circuits. - M .: Owls. radio, 1979, 336 p. /;
a ferrozoid, as two windings on a core made of permalloy with a hysteresis loop with a rectangular coefficient close to unity;
controlled current source as an amplifier with current feedback according to / Falkenberry L. Application of operational amplifiers and linear ICs: Transl. from English. - M.- Mir, 1985.572 s./.

 Experimental studies of the layout of the inventive device for measuring magnetic field strength showed that, in comparison with a device of a similar purpose (prototype), the inventive device provides improved performance by maintaining the duty cycle of compensating pulses proportional to their amplitude.

Claims (1)

 A device for measuring magnetic field strength, containing a rectangular pulse generator, a flux gate with a core made of permalloy with a hysteresis loop with a square factor close to unity, to the output winding of which an integrator is connected, with an output connected to the input of the amplifier, the output of which is connected to the input of the threshold block connected in series with the first logical element AND, the first reversible pulse counter, digital-to-analog converter, controlled current source, key and winding and excitation of a flux gate, the second input of the first reversible pulse counter and the first input of the first logic element And connected to the output of the threshold block, characterized in that it is equipped with a second logic element And and the second reversible pulse counter, and the output of the generator is connected to the first inputs of the second logic element And and the second reversible pulse counter, the output of the second logical element And is connected to the second inputs of the first logical element And, the second reverse pulse counter and CL On the other hand, the third input of the second reversible pulse counter is connected to the output of the first reversible pulse counter, and the output is to the second input of the second logic element I.

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